What causes hot melt adhesive to bubble during baking?
Bubbling during hot melt adhesive baking is a common problem that may be caused by a variety of factors. The following are the main reasons and solutions:
1. Moisture or volatile substances
Cause: Hot melt adhesive contains moisture or volatile substances, which evaporate to form bubbles after heating.
Solution:
Make sure the hot melt adhesive is dry before use.
Avoid humid environments during storage.
Choose hot melt adhesive with low volatility.
2. Too high temperature
Cause: The baking temperature is too high, causing the hot melt adhesive to overheat and decompose locally to produce gas.
Solution:
Strictly control the baking temperature to avoid exceeding the recommended range.
Use temperature control equipment and monitor in real time.
3. Uneven heating
Cause: Uneven heating causes local overheating or underheating, causing bubbles.
Solution:
Ensure that the heating equipment is heated evenly.
Stir or flip appropriately during heating.
4. Too thick adhesive layer
Reason: The adhesive layer is too thick, the internal heating is uneven, and the external part solidifies first, which hinders the internal gas from escaping.
Solution:
Control the thickness of the adhesive layer to avoid too thick.
Apply in layers and bake layer by layer.
5. Substrate problem
Reason: There are pollutants or pores on the surface of the substrate, which release gas when heated.
Solution:
Clean the surface of the substrate to ensure that there are no pollutants.
Pretreat the porous substrate, such as applying primer.
6. Glue quality problem
Reason: The quality of the hot melt adhesive itself, such as impurities or improper formulation.
Solution:
Choose a hot melt adhesive with reliable quality.
Check the glue for impurities before use.
7. Insufficient baking time
Reason: Insufficient baking time, the glue is not completely cured, and the residual gas forms bubbles.
Solution:
Ensure sufficient baking time.
Adjust the time according to the type and thickness of the glue.